Time Machine using OSX Mavericks

I am running 4.2.25-RC1 firmware on my Ultra 4 Plus and have a new MacBook Pro. When I setup a new time machine sparsebundle through Frontview, I fill 1500 GB in the capacity field and click apply. Spinning wheel goes on indefinitely and I eventually have to refresh the webpage. Go to Time Machine to start a new backup and the maximum size of the backup is shown to be the full capacity of my NAS and not the capacity I set in Frontview for the Time Machine Backup. Looking at the sparsebundle in OS X disk utility confirms that the maximum capacity of the sparsebundle is the full capacity of the NAS. Tried reinstalling firmware and problem persists. Also tried deleting sparsebundle and starting over and same issue. Looks like the beta firmware has an issue setting the capacity of the Time Machine sparsebundle file during its creation.

Any advice as how to workaround this would be appreciated as I don't want my time machine backup to take up the entire NAS.